Define "spark killer". Never heard this term, no proper results in Google except some trivial RC snubber things.
Seeing sparks on some power supplies (like laptop / phone chargers) is normal and due to the design of said chargers. You can't do anything about it.
"Your house wiring is sparking and your house is on fire soon" detectors also exist, detecting longer term sparking and disconnecting the whole house supply / some circuits of it. The problem with these is the potential for false positives. Generally, it's a better idea to rebuild very old / faulty house wiring. But this has nothing to do with sparking you see while plugging in devices.